Serious injury triggers safeguard investigations when domestic producers show increased imports, injury and a causal link. Initiation of safeguard investigations requires a written application by or on behalf of the domestic producer alleging serious injury or threat of serious injury from increased imports, supported by evidence of increased imports, injury or threat, and a causal link, plus a statement on adjustment measures; the Director General must verify the accuracy and adequacy of that evidence before initiating an investigation, and may also initiate suo motu if satisfied that the evidentiary thresholds are met.